Ballast, I think it's too soon to conclude she's not interested. She could be taking time to think about what she wants. She could be talking to another guy and she's waiting to see how it turns out with him. She may be shy or lack self confidence to meet in person. Maybe she really is busy. Or maybe she doesn't want to move fast. I agree with letting her go since it won't benefit you to keep waiting for her. But what did you say to her or ask her when you chatted on Saturday? Did you ask if she wants to meet?
I have my daughter 100% of the time. I can't imagine how hard it must be to have your daughter part-time. This is one of the main reasons why I would do anything to save my marriage because it's so hard for us and so hard for our children to go back-and-forth. I know everyone gets used to it eventually, but it's especially cruel and difficult in the beginning.